Fixing device

Abstract

To provide a fixing device having high durability.SOLUTION: A fixing device of an embodiment has a cylindrical body, a heat generating slide member, a holder, a sensor, a pressure roller, a pressure mechanism, and a moving mechanism. The heat generating slide member is arranged inside the cylindrical body. The heat generating slide member has a longitudinal direction that is an axial direction of the cylindrical body. The heat generating slide member has a heat generation area for generating heat upon energization. The holder holds the heat generating slide member. The sensor is in contact with the heat generating slide member to detect a temperature of the heat generating slide member. The pressure roller is in contact with an outer peripheral surface of the cylindrical body to form a nip between the cylindrical body and the pressure roller. The pressure mechanism can make a transition to a first state and a second state. In the first state, the cylindrical body and the pressure roller form the nip. In the second state, the cylindrical body and the pressure roller are in contact with each other, and a force applied to both the cylindrical body and the pressure roller is smaller than that in the first state. The moving mechanism causes the pressure mechanism to make a transition to the first state and the second state.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] An embodiment of the present invention relates to a fixing device. [Background technology]

[0002] 2. Description of the Related Art Image forming apparatuses that form images on sheets are used as image processing apparatuses. The image forming apparatuses have a fixing device that fixes toner onto the sheets. The fixing device is required to have improved durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-304866 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a fixing device having high durability. [Means for solving the problem]

[0005] The fixing device according to the first aspect has a cylindrical body, a heat-generating sliding member, a holder, a sensor, a pressure roller, a pressure mechanism, and a moving mechanism. The cylindrical body is in the form of a film. The heat-generating sliding member is disposed inside the cylindrical body. The heat-generating sliding member has a heat-generating region that generates heat when electricity is applied thereto. The holder holds the heat-generating sliding member. The sensor contacts the heat-generating sliding member to detect the temperature of the heat-generating sliding member. The pressure roller contacts the outer circumferential surface of the cylindrical body to form a nip between the cylindrical body and the pressure roller. The pressure mechanism can transition between a first state and a second state. In the first state, a nip is formed by the cylindrical body and the pressure roller. In the second state, the cylindrical body and the pressure roller are in contact with each other, and a force applied to the cylindrical body and the pressure roller is smaller than that in the first state. The moving mechanism causes the pressure mechanism to transition between the first state and the second state.

[0006] A fixing device according to a second aspect is the fixing device according to the first aspect, wherein the pressure mechanism supports the pressure roller so that it can rotate on its own axis and move in a direction perpendicular to the axial direction, and the moving mechanism includes a cam follower arranged in the pressure mechanism, a cam having a cam surface abutting the cam follower and rotatable on its own axis, and cooperating with the cam follower to move the pressure roller in the perpendicular direction via the pressure mechanism, a small diameter portion of the cam surface having the smallest outer diameter abuts the cam follower in the second state, and a driving source that rotates the cam in one direction.

[0007] A fixing device according to a third aspect is the fixing device according to the first or second aspect, wherein the holder holds the heat-generating sliding member such that a gap is formed between the heat-generating sliding member and the holder in an area overlapping with the heat-generating region in the axial direction when the pressure roller is separated from the cylindrical body.

[0008] A fixing device according to a fourth aspect is a fixing device according to any one of the first to third aspects, further comprising a heater unit and a heat transfer member, the heat transfer member being between the heater unit and the holder.

[0009] A fixing device according to a fifth aspect is the fixing device according to the third or fourth aspect, wherein the heat-generating sliding member is held by the holder outside the heat-generating region in the axial direction.

[0010] A fixing device according to a sixth aspect is the fixing device according to the fifth aspect, wherein the sensor is biased toward the heat-generating sliding member relative to the holder, and the heat-generating sliding member is pressed toward the pressure roller by the sensor. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an image processing apparatus according to an embodiment. [Diagram 2] FIG. 1 is a diagram showing a hardware configuration of an image forming apparatus according to an embodiment. [Diagram 3]FIG. 2 is a front sectional view of the fixing device according to the first embodiment. [Figure 4] 6 is a front cross-sectional view of the heater unit taken along line IV-IV in FIG. 5. [Diagram 5] FIG. 4 is a bottom view of the heater unit according to the first embodiment. [Figure 6] FIG. [Figure 7] 7 is a cross-sectional view of the film unit taken along line VII-VII in FIG. 3. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 7 is a cross-sectional view of the fixing device taken along line VII-VII in FIG. [Figure 11] FIG. 4 is a block diagram showing the functional configuration of a control unit. [Figure 12] FIG. 11 is a bottom view of the heater unit according to the second embodiment. [Figure 13] FIG. 13 is a bottom view of the heater unit according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a fixing device according to an embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals, and redundant description of those components may be omitted.

[0013] FIG. 1 is a schematic diagram of an image processing apparatus according to an embodiment. The image processing device according to this embodiment is, for example, an image forming device 1 such as a multifunction peripheral (MFP) printer or copier. For example, the image forming device 1 is installed in a workplace. The image forming device 1 performs a process of forming an image on a sheet S. The sheet S may be paper. The image forming device 1 has a housing 10, a scanner section 2, an image forming unit 3, a sheet supply section 4, a conveying section 5, a paper output tray 7, a reversing unit 9, a control panel 8, and a control section 6.

[0014] The housing 10 forms the outer shape of the image forming apparatus 1 . The scanner unit 2 reads image information of an object to be copied as light and shade, and generates an image signal. The scanner unit 2 outputs the generated image signal to the image forming unit 3. The image forming unit 3 forms a toner image using a recording agent such as toner, based on an image signal received from the scanner unit 2 or an image signal received from an external source. The image forming unit 3 transfers the toner image onto the surface of the sheet S. The image forming unit 3 applies heat and pressure to the toner image on the surface of the sheet S to fix the toner image to the sheet S. Details of the image forming unit 3 will be described later.

[0015] The sheet supply section 4 supplies the sheets S one by one to the conveying section 5 in accordance with the timing at which the image forming unit 3 forms a toner image. The sheet supply section 4 includes a sheet storage section 20 and a pickup roller . The sheet storage section 20 stores sheets S of a predetermined size and type. The pickup roller 21 picks up the sheets S one by one from the sheet storage unit 20. The pickup roller 21 supplies the picked-up sheets S to the conveying unit 5.

[0016] The conveying section 5 conveys the sheet S supplied from the sheet supplying section 4 to the image forming unit 3. The conveying section 5 includes a conveying roller 23 and a registration roller 24. The conveying roller 23 conveys the sheet S supplied from the pickup roller 21 to the registration roller 24. The conveying roller 23 abuts the leading edge of the sheet S in the conveying direction against the nip N of the registration roller 24. The registration rollers 24 adjust the position of the leading edge of the sheet S in the conveying direction by bending the sheet S at the nip N. The registration rollers 24 convey the sheet S in accordance with the timing at which the image forming unit 3 transfers a toner image onto the sheet S.

[0017] The image forming unit 3 will now be described. The image forming unit 3 includes a plurality of image forming sections 25, a laser scanning unit 26, an intermediate transfer belt 27, a transfer section 28, and a fixing device 30. The image forming unit 25 has a photoconductor drum 29. The image forming unit 25 forms a toner image on the photoconductor drum 29 in response to an image signal from the scanner unit 2 or an external device. The multiple image forming units 25 form toner images using yellow, magenta, cyan, and black toners, respectively.

[0018] A charger, a developer, and the like are arranged around the photoconductor drum 29. The charger charges the surface of the photoconductor drum 29. The developer contains developer including yellow, magenta, cyan, and black toner. The developer develops the electrostatic latent image on the photoconductor drum 29. As a result, a toner image made of toner of each color is formed on the photoconductor drum 29.

[0019] The laser scanning unit 26 scans the charged photoconductor drum 29 with laser light L to expose the photoconductor drum 29. The laser scanning unit 26 exposes the photoconductor drum 29 of the image forming section 25 for each color with separate laser light LY, LM, LC, and LK. In this way, the laser scanning unit 26 forms an electrostatic latent image on the photoconductor drum 29.

[0020] The toner image on the surface of the photosensitive drum 29 is primarily transferred onto the intermediate transfer belt 27 . The transfer unit 28 transfers the toner image, which has been primarily transferred onto the intermediate transfer belt 27, onto the front surface of the sheet S at a secondary transfer position. The fixing device 30 applies heat and pressure to the toner image transferred to the sheet S, thereby fixing the toner image to the sheet S. The fixing device 30 will be described in detail later.

[0021] The reversing unit 9 reverses the sheet S to form an image on the back side of the sheet S. The reversing unit 9 reverses the sheet S discharged from the fixing device 30 by switchback. The reversing unit 9 conveys the reversed sheet S toward the registration rollers 24. The sheet discharge tray 7 holds the sheet S on which an image has been formed and discharged. The control panel 8 is a part of an input unit through which an operator inputs information for operating the image forming apparatus 1. The control panel 8 has a touch panel and various hard keys. The control unit 6 controls each unit of the image forming apparatus 1 .

[0022] FIG. 2 is a diagram showing the hardware configuration of the image forming apparatus according to the embodiment. 2, the image forming apparatus 1 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, and the like, which are connected via a bus, and executes a program. The image forming apparatus 1 functions as an apparatus including a scanner section 2, an image forming unit 3, a sheet supply section 4, a conveying section 5, a reversing unit 9, a control panel 8, and a communication section 90 by executing the program.

[0023] The CPU 91 functions as a control unit 6 by executing programs stored in the memory 92 and the auxiliary storage device 93. The control unit 6 controls the operation of each functional unit of the image forming apparatus 1. The functional configuration of the control unit 6 will be described later. The auxiliary storage device 93 is configured using a storage device such as a magnetic hard disk device, a semiconductor storage device, etc. The auxiliary storage device 93 stores information. The communication unit 90 includes a communication interface for connecting the device to an external device, and communicates with the external device via the communication interface.

[0024] (First embodiment) The fixing device 30 of the first embodiment will be described. FIG. 3 is a front cross-sectional view of the fixing device according to the first embodiment. As shown in FIG. 3, the fixing device 30 includes a pressure roller 31, a film unit 35, a pressure mechanism 70, a moving mechanism 80, and a frame 34. A fixing nip FN is formed between the pressure roller 31 and the film unit 35. The pressure roller 31 presses the toner image on the sheet S that has entered the fixing nip FN. The pressure roller 31 rotates to transport the sheet S. The film unit 35 heats the toner image on the sheet S that has entered the fixing nip FN. The frame 34 is fixed to the housing 10 of the image forming apparatus 1. The frame 34 supports the pressure roller 31, the film unit 35, and the moving mechanism 80.

[0025] In this application, the z direction, x direction, and y direction are defined as follows. The z direction is the direction in which the pressure roller 31 and the film unit 35 are aligned. The +z direction is the direction from the film unit 35 toward the pressure roller 31. The x direction is the transport direction of the sheet S in the fixing nip FN, and the +x direction is the downstream side of the transport direction of the sheet S. The y direction is the direction perpendicular to the z direction and the x direction, and is the axial direction of the pressure roller 31.

[0026] The pressure roller 31 is rotatable around a pressure roller rotation center rc The pressure roller 31 has a core metal 32, an elastic layer 33, and a release layer.

[0027] The core 32 is formed into a cylindrical shape from a metal material such as stainless steel. Both axial ends of the core 32 are rotatably supported. The core 32 is rotated by a motor. The core 32 abuts against a cam member. The cam member moves the core 32 toward and away from the film unit 35 as it rotates.

[0028] The elastic layer 33 is made of an elastic material such as silicone rubber, etc. The elastic layer 33 is formed on the outer circumferential surface of the core metal 32 with a constant thickness. The release layer is formed of a resin material such as PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer), etc. The release layer is formed on the outer peripheral surface of the elastic layer 33. The hardness of the outer peripheral surface of the pressure roller 31 is desirably 40° to 70° when a load of 9.8 N is applied thereto using an ASKER-C hardness tester. This ensures the area of ​​the fixing nip FN and the durability of the pressure roller 31.

[0029] The pressure roller 31 is rotated by a motor to rotate on its axis. When the pressure roller 31 rotates on its axis with the fixing nip FN formed, the cylindrical body 37 of the film unit 35 is rotated accordingly. The pressure roller 31 rotates on its axis with the sheet S disposed in the fixing nip FN, thereby conveying the sheet S in the conveying direction W.

[0030] The film unit 35 has a cylindrical body 37 , a heat generating sliding member 36 , a holder 38 , a stay 39 , a temperature sensing element 60 , and a film thermometer 64 .

[0031] The cylindrical body 37 is a fixing belt. The cylindrical body 37 is a cylindrical film extending along the y direction. The cylindrical body 37 has, in order from the inner periphery, a base layer, an elastic layer 33, and a release layer. The base layer is formed into a cylindrical shape from a material such as polyimide. The elastic layer 33 is laminated on the outer periphery of the base layer. The elastic layer 33 is formed from an elastic material such as silicone rubber. The release layer is laminated on the outer periphery of the elastic layer 33. The release layer is formed from a material such as PFA resin.

[0032] The heat generating sliding member 36 is disposed inside the cylindrical body 37. The heat generating sliding member 36 includes a heater unit 40 and a heat transfer member 65.

[0033] The heater unit 40 is formed in a rectangular plate shape with the y direction as the longitudinal direction and the x direction as the transverse direction. In the x and y directions, the direction approaching the center of the heater unit 40 may be referred to as the inside, and the direction away from the center of the heater unit 40 may be referred to as the outside. The heater unit 40 has a first surface 41 in the +z direction and a second surface 42 facing the opposite side to the first surface 41. The first surface 41 of the heater unit 40 heats the cylindrical body 37. The first surface 41 contacts the inner surface of the cylindrical body 37 via grease 47.

[0034] Fig. 4 is a front cross-sectional view of the heater unit taken along line IV-IV in Fig. 5. Fig. 5 is a bottom view (viewed from the +z direction) of the heater unit of the first embodiment. As shown in FIGS. 4 and 5, the heater unit 40 includes a substrate 43, a heat generating region 45, and a wiring set 55. The substrate 43 includes a heat generating region 45 and a wiring set 55. As shown in FIG.

[0035] The substrate 43 is formed of a metal material such as stainless steel, or a ceramic material such as aluminum nitride. The substrate 43 is a rectangular plate with the y direction as the longitudinal direction and the x direction as the transverse direction. An insulating layer 44 made of a glass material or the like is formed on the +z direction surface of the substrate 43. The -z direction surface of the substrate 43 is the second surface 42 of the heater unit 40. The second surface 42 of the heater unit 40 is formed in a planar shape perpendicular to the z direction.

[0036] As shown in FIG. 5, the heat generating region 45 is disposed on the substrate 43. The heat generating region 45 has at least one heat generating element 50. The heat generating element 50 is formed by disposing a material such as a silver-palladium alloy on the substrate 43 by screen printing. The heat generating region 45 is defined between both ends of all the heat generating elements 50 in the y direction and between both ends in the x direction. The overall outer shape of the heat generating region 45 is formed into a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. The heat generating region 45 is disposed inside both ends of the substrate 43.

[0037] The heat generating region 45 of this embodiment has a plurality of heat generating elements 50. The plurality of heat generating elements 50 have a first end heat generating element 51, a central heat generating element 52, and a second end heat generating element 53, which are arranged side by side in the y direction. The central heat generating element 52 is arranged in the center of the heat generating region 45 in the y direction. The central heat generating element 52 may be formed by combining a plurality of small heat generating elements arranged side by side in the y direction. The first end heat generating element 51 is arranged in the +y direction of the central heat generating element 52, at the end of the heat generating region 45 in the +y direction. The second end heat generating element 53 is arranged in the -y direction of the central heat generating element 52, at the end of the heat generating region 45 in the -y direction.

[0038] Wires of a wiring set 55 are connected to each heating element 50. The heating region 45 generates heat when current is applied via the wiring set 55. A sheet S having a small width in the y direction passes through the center of the fixing device 30 in the y direction. In this case, the control unit 6 causes only the central heating element 52 located on the inside among the multiple heating elements 50 to generate heat. On the other hand, in the case of a sheet S having a large width in the y direction, the control unit 6 causes all of the heating elements 50 to generate heat.

[0039] 4, the heating element 50 and the wiring set 55 are formed on the surface of the insulating layer 44 in the +z direction. A protective layer 46 is formed of a glass material or the like so as to cover the heating element 50 and the wiring set 55. The protective layer 46 forms the first surface 41 of the heater unit 40. When the heater unit 40 generates heat, the viscosity of the grease 47 between the protective layer 46 and the cylindrical body 37 decreases, thereby ensuring the sliding properties between the heater unit 40 and the cylindrical body 37.

[0040] Similar to the insulating layer 44 formed in the +z direction of the substrate 43, the insulating layer 44 may be formed in the -z direction of the substrate 43. Similar to the protective layer 46 formed in the +z direction of the substrate 43, the protective layer 46 may be formed in the -z direction of the substrate 43. This suppresses warping of the substrate 43.

[0041] 3, the entire heat generating region 45 is included within the area of ​​the fixing nip FN and is disposed at the center of the fixing nip FN, so that the heat distribution in the fixing nip FN becomes uniform, and the sheet S passing through the fixing nip FN is heated uniformly.

[0042] The heat transfer member 65 is made of a material having a higher thermal conductivity than the substrate 43. For example, the heat transfer member 65 is made of a metal material such as copper or aluminum, or a graphite sheet. The heat transfer member 65 overlaps the heater unit 40. The heat transfer member 65 is a rectangular plate corresponding to the outer shape of the substrate 43 of the heater unit 40. The heat transfer member 65 overlaps all the heating elements 50 in a plan view seen from the z direction (see FIG. 5). The heat transfer member 65 contacts at least a portion of the second surface 42 of the heater unit 40. The heat transfer member 65 equalizes the temperature distribution of the heater unit 40.

[0043] The holder 38 is made of a resin material such as a liquid crystal polymer. The holder 38 has a length in the y direction. The holder 38 is arranged so as to cover both sides of the heater unit 40 in the -z direction and in the x direction. The holder 38 holds the heat generating sliding member 36. The holder 38 holds only both ends of the substrate 43 of the heater unit 40 in the y direction so that the substrate 43 cannot be separated in the +z direction, with the heat transfer member 65 sandwiched between the holder 38 and the heater unit 40. Both ends of the holder 38 in the x direction are rounded. The holder 38 supports the inner circumferential surface of the cylindrical body 37 at both ends of the heater unit 40 in the x direction.

[0044] The holder 38 includes a base 381, an upstream wall 382, ​​and a downstream wall 383. The base 381 supports the heat-generating sliding member 36 from the second surface 42 side of the heater unit 40. The holder 38 sandwiches an insulating sheet between the base 381 and the heat transfer member 65. For example, the insulating sheet is a polyimide sheet. The upstream wall 382 protrudes from the end of the base 381 in the -x direction toward the pressure roller 31. The downstream wall 383 protrudes from the end of the base 381 in the +x direction toward the pressure roller 31. The heat-generating sliding member 36 is disposed between the upstream wall 382 and the downstream wall 383. The edges of the upstream wall 382 and the downstream wall 383 in the +z direction each extend in the y direction. The +z-direction edges of the upstream wall portion 382 and the downstream wall portion 383 are located at approximately the same position as the first surface 41 of the heater unit 40 in the z direction.

[0045] The stay 39 is formed of a steel plate material or the like. The stay 39 has a length in the y direction. The cross section of the stay 39 perpendicular to the y direction is U-shaped. The stay 39 is attached to the holder 38 in the -z direction so that the opening of the U is closed by the base 381 of the holder 38. Both ends of the stay 39 in the y direction are fixed to the frame 34. The stay 39 improves the bending rigidity of the film unit 35.

[0046] The temperature sensor 60 is disposed in the -z direction of the heater unit 40. The temperature sensor 60 is disposed within a range overlapping with the heat generating region 45 in the y direction. The temperature sensor 60 contacts the surface of the heat transfer member 65 in the -z direction via an insulating sheet interposed between the base 381 of the holder 38 and the heat transfer member 65. The temperature sensor 60 is disposed inside a hole 384 that penetrates the base 381 of the holder 38 in the z direction. The wiring of the temperature sensor 60 is drawn out in the -z direction from the hole 384 of the holder 38. The temperature sensor 60 is a heater thermometer 61 and a thermostat 62. The heater thermometer 61 is a thermistor.

[0047] 6 is a plan view (viewed from the -z direction) of the heater thermometer and the thermostat. In FIG. 6, the holder 38 is omitted. As shown in FIG. 6, the heater thermometer 61 detects the temperature of the heat-generating sliding member 36. The heater thermometer 61 detects the temperature of the heater unit 40 via the heat transfer member 65. The heater thermometer 61 has a central heater thermometer 611 and an end heater thermometer 612. The thermostat 62 has a central thermostat 621 and an end thermostat 622. The central heater thermometer 611 and the central thermostat 621 are arranged in the -z direction of the central heating element 52. Meanwhile, the end thermostat 622 and the end heater thermometer 612 are arranged in the -z direction of the first end heating element 51 and the second end heating element 53.

[0048] Each of the temperature sensing elements 60 is biased in the +z direction by a biasing member so as to protrude from the hole 384 of the holder 38 towards the heater unit 40. Each of the temperature sensing elements 60 presses the heat generating sliding member 36 in the +z direction against the holder 38. The temperature sensing elements 60 press the heat transfer member 65 in the +z direction, thereby indirectly pressing the heater unit 40 in the +z direction against the holder 38.

[0049] FIG. 7 is a cross-sectional view of the film unit taken along line VII-VII in FIG. As shown in FIG. 7, when the pressure roller 31 is separated from the film unit 35, the heat-generating sliding member 36 is pressed by the temperature-sensing element 60 and separates from the base 381 of the holder 38. As both ends of the heater unit 40 in the y direction are held by the holder 38, the heat-generating sliding member 36 is bent so that a gap is formed between the entire area overlapping with the heat-generating region 45 in the y direction and the base 381 of the holder 38. The cylindrical body 37 has a contact portion 371 that contacts the center of the heat-generating sliding member 36 in the y direction. The cylindrical body 37 is pressed by the center of the heat-generating sliding member 36 in the y direction to form a gap between the cylindrical body 37 and the heater unit 40. The gap between the cylindrical body 37 and the heater unit 40 expands from the contact portion 371 toward the outside in the y direction.

[0050] 6, when the temperature of the heater unit 40 detected via the heat transfer member 65 exceeds a predetermined temperature, the thermostat 62 cuts off the power supply to the heating element 50. As a result, excessive heating of the cylindrical body 37 by the heater unit 40 is suppressed.

[0051] 3, the film thermometers 64 are in contact with a portion of the inner circumferential surface of the cylindrical body 37. The film thermometers 64 are arranged at intervals in the y direction. The film thermometers 64 detect the temperatures of different portions of the cylindrical body 37 in the y direction.

[0052] FIG. 8 is a front view of the fixing device. As shown in FIG. 8, the pressure mechanism 70 presses the pressure roller 31 toward the cylindrical body 37. The pressure mechanism 70 displaces the pressure roller 31 relative to the cylindrical body 37 so that the pressure roller rotation center rc approaches and moves away from the cylindrical body 37 while the pressure roller 31 is in contact with the cylindrical body 37. The pressure mechanism 70 can transition between a first state in which a fixing nip FN is formed between the pressure roller 31 and the cylindrical body 37, and a second state in which a force applied to the cylindrical body 37 and the pressure roller 31 is smaller than that in the first state. The pressure mechanism 70 shown in FIG. 8 is in the first state. The fixing nip FN is defined as a state in which the fixing device 30 can perform a fixing operation of a toner image on a sheet S. The second state corresponds to an energy saving mode or a sleep state. For example, the sleep state is a state in which the memory 92 is energized but the heater unit 40 is not energized. In the second state, the pressure of the pressure roller 31 against the cylindrical body 37 is relaxed, so that the plastic deformation of the cylindrical body 37 is prevented.

[0053] The pressure mechanism 70 has an arm 71, a pusher 72, a pin 73, and an elastic member 74. The components of the pressure mechanism 70 are located at both ends of the pressure roller 31 in the y direction. The pressure mechanism 70 is plane-symmetric with respect to the xz plane that passes through the center point of the pressure roller 31 in the y direction. The components of the pressure mechanism 70 located in the +y direction of the pressure roller 31 will be described below.

[0054] The arm 71 has a length in the x direction. The arm 71 may be made of a steel plate material or the like. The arm 71 is rotatable around an arm rotation center ac. The arm rotation center ac is located near the end of the arm 71 in the -x direction and is parallel to the y direction.

[0055] The arm 71 has an arm main body plate 711 and an arm connecting portion 712 . The arm body plates 711 are parallel to the xz plane. The pair of arm body plates 711 are spaced apart in the y direction. The arm body plate 711 in the -y direction has a semicircular notch that rotatably supports the pressure roller 31. The arm connectors 712 connect the -z direction ends of the pair of arm body plates 711 to each other. The arm connectors 712 are located at both ends of the arm 71 in the x direction.

[0056] The pusher 72 may be formed of a steel plate material or the like. The pusher 72 is rotatable around an arm rotation center ac. The arm rotation center ac is located at the middle of the pusher 72 in the x direction. One side of the pusher 72 has a length in the +x direction from the arm rotation center ac. The other side of the pusher 72 has lengths in the -x and -z directions from the arm rotation center ac.

[0057] The pusher 72 has a pusher main body plate 721 and a pusher connecting portion 722 . The pusher body plates 721 are parallel to the xz plane. The pair of pusher body plates 721 are spaced apart in the y direction. The pair of pusher body plates 721 are located inside the pair of arm body plates 711 in the y direction. The pusher connecting portion 722 connects the ends of the pair of pusher body plates 721 in the +z direction to each other.

[0058] The pin 73 is at the +x-direction end of the arm 71 and the pusher 72. The pin 73 extends along the z-direction. The pin 73 has a body portion 731 and a head portion 732. Body 731 is in the shape of a round bar. A first end of body 731 in the -z direction is fixed to arm connector 712 by screwing or the like. Body 731 has a length in the +z direction from arm connector 712 toward pusher connector 722. Body 731 is inserted into a through hole formed in pusher connector 722, and has a length up to pusher connector 722 in the +z direction. The head 732 is located at a second end in the +z direction of the body 731. The head 732 has a larger diameter than the through hole of the pusher connecting portion 722.

[0059] The elastic member 74 is supported by the pin 73. The elastic member 74 is on the same side (+x direction) as the pressure roller rotation center rc with respect to the arm rotation center ac. The elastic member 74 is between the arm 71 and the pusher 72. In a compressed state, the elastic member 74 is between the arm connecting portion 712 and the pusher connecting portion 722. The elastic member 74 biases the arm 71 in the direction in which the pressure roller 31 abuts against the cylindrical body 37. The elastic member 74 is a coil spring. The elastic member 74 is fitted onto the body portion 731 of the pin 73.

[0060] The moving mechanism 80 transitions the pressure mechanism 70 between the first state and the second state. The pressure mechanism 70 can only take a state between the first state and the second state by the operation of the moving mechanism 80. The moving mechanism 80 includes a cam follower 81, a cam 82, and a driving source 83. The cam follower 81 and the cam 82 are located at both ends of the pressure roller 31 in the y direction. The cam follower 81 is plane-symmetric with respect to an xz plane passing through the center point of the pressure roller 31 in the y direction. The cam 82 is plane-symmetric with respect to an xz plane passing through the center point of the pressure roller 31 in the y direction. The cam follower 81 and the cam 82 in the +y direction of the pressure roller 31 will be described below.

[0061] The cam follower 81 is located at the -x direction and -z direction ends of the pusher 72. The cam follower 81 is cylindrical and located between a pair of pusher body plates 721. The cam follower 81 is a roller that can rotate around a cam follower rotation center fc that is parallel to the y direction.

[0062] The cam 82 is adjacent to the cam follower 81 and is in the +x direction of the cam follower 81. The cam 82 is rotatable around a cam rotation center cc. A cam surface 84 that constitutes the contour of the cam 82 is capable of abutting against the outer circumferential surface of the cam follower 81. A pair of cams 82 at both ends of the pressure roller 31 in the y direction are connected by a cam shaft having a length in the y direction. The cam rotation center cc is on the opposite side of the pressure roller rotation center rc across the arm rotation center ac. The cam 82 receives the output of the drive source 83 and rotates around the cam rotation center cc only in the direction of the arrow C. The rotation angle of the cam 82 is detected by a sensor.

[0063] The cam surface 84 is formed such that the distance to the cam rotation center cc changes according to the rotation angle of the cam 82. Hereinafter, the distance from the cam rotation center cc to the cam surface 84 is referred to as the outer diameter. The cam surface 84 includes a large diameter portion 841 having the largest outer diameter of the cam surface 84, and a small diameter portion 842 having the smallest outer diameter of the cam surface 84. The cam surface 84 extends continuously from the large diameter portion 841 to the small diameter portion 842 in the opposite direction to the rotation direction of the cam 82. The outer diameter of the cam surface 84 gradually decreases from the large diameter portion 841 to the small diameter portion 842 in the opposite direction to the rotation direction of the cam 82. The cam surface 84 allows the cam follower 81 to roll continuously over the entire circumference as the cam 82 rotates.

[0064] The driving source 83 rotates a camshaft connecting the pair of cams 82 via a worm gear or the like. The driving source 83 rotates the pair of cams 82 by driving the camshaft. The driving source 83 rotates the cams 82 in only one direction around a cam rotation center cc. The driving source 83 is controlled by the control unit 6.

[0065] The operation of the pressure mechanism 70 will now be described. When performing a fixing operation in the fixing device 30, the movement mechanism 80 brings the pressure roller 31 into contact with the cylindrical body 37. Fig. 8 shows a first state in which the pressure roller 31 is in contact with the cylindrical body 37. In the first state, the cam 82 is in contact with the large diameter portion 841 of the cam follower 81. In the first state, a fixing nip FN is formed by the cylindrical body 37 and the pressure roller 31. In the first state, the pressure roller 31 is elastically deformed.

[0066] FIG. 9 is an explanatory diagram of the operation of the pressure mechanism. The pressure mechanism 70 shown in FIG. 9 is in the second state. The cam 82 abuts against the small diameter portion 842 of the cam follower 81 in the second state. In the second state, the cylindrical body 37 and the pressure roller 31 are in contact with each other, and the force acting between the cylindrical body 37 and the pressure roller 31 is smaller than that in the first state. In the second state, the width in the x direction of the nip formed by the cylindrical body 37 and the pressure roller 31 is smaller than the width in the x direction of the fixing nip FN. In the second state, the pressure roller 31 may be elastically deformed.

[0067] The transition operation between the first state and the second state by the moving mechanism 80 will be described. In the first state shown in FIG. 8, the pressure roller 31 is elastically deformed by a reaction force pressing the cylindrical body 37 between the pressure roller 31 and the heater unit 40. A force in the +z direction is applied to the pressure roller 31 by a restoring force of the elastic deformation. When the force in the +z direction is applied to the pressure roller 31, the pressure roller 31 pushes the arm 71 around the arm rotation center ac in the direction of the arrow A. The arm 71 pushed by the pressure roller 31 pushes the pusher 72 around the arm rotation center ac in the direction of the arrow A via the compressed elastic member 74, and presses the cam follower 81 against the cam 82. The pusher 72 presses the pressure roller 31 against the cylindrical body 37 via the elastic member 74 and the arm 71 due to the reaction force of pressing the cam follower 81 against the cam 82.

[0068] From the first state, the cam 82 rotates around the cam rotation center cc in the direction of the arrow C. The cam follower 81 moves relatively along the cam surface 84 of the cam 82 from the large diameter portion 841 toward the small diameter portion 842, and approaches the cam rotation center cc. The pusher 72 is permitted to rotate around the arm rotation center ac in the direction of the arrow A. The pusher 72 rotates around the arm rotation center ac in the direction of the arrow A due to the restoring force of the elastic member 74. Simultaneously with the rotation of the pusher 72, the arm 71 rotates around the arm rotation center ac in the direction of the arrow A so that the restoring force of the elastic member 74 and the restoring force of the pressure roller 31 are balanced. By the arm 71 rotating around the arm rotation center ac in the direction of the arrow A, the pressure roller 31 is displaced in the +z direction so as to move the pressure roller rotation center rc away from the film unit 35.

[0069] When the cam 82 further rotates around the cam rotation center cc in the direction of the arrow C, the pusher 72 rotates around the arm rotation center ac in the direction of the arrow A. The cam follower 81 abuts against the small diameter portion 842 of the cam surface 84 of the cam 82, and the pusher 72 enters a second state in which it has fully rotated around the arm rotation center ac in the direction of the arrow A. In the second state, the pressure roller 31 is in contact with the cylindrical body 37 over the entire length in the y direction. The pressure roller 31 applies less force to the cylindrical body 37 compared to the first state. In the second state, the pressure roller 31 presses the heater unit 40 and the heat transfer member 65 in the -z direction via the cylindrical body 37 so that no gap is formed between the heat transfer member 65 and the base portion 381 of the holder 38.

[0070] From the second state, the cam 82 rotates around the cam rotation center ccc in the direction of the arrow C. The cam follower 81 moves relatively along the cam surface 84 of the cam 82 from the small diameter portion 842 toward the large diameter portion 841, while moving away from the cam rotation center cc. The pusher 72 rotates around the arm rotation center ac in the direction of the arrow B while compressing the elastic member 74. At the same time as the pusher 72 rotates, the arm 71 receives the restoring force of the elastic member 74 and rotates around the arm rotation center ac in the direction of the arrow B. The arm 71 rotates around the arm rotation center ac in the direction of the arrow B, thereby pressing the pressure roller 31 against the cylindrical body 37. By being pressed against the cylindrical body 37, the pressure roller 31 is displaced in the -z direction so as to bring the pressure roller rotation center rc closer to the film unit 35.

[0071] When the cam 82 further rotates around the cam rotation center cc in the direction of the arrow C, the pusher 72 rotates around the arm rotation center ac in the direction of the arrow B. The cam follower 81 abuts against the large diameter portion 841 of the cam surface 84 of the cam 82, and the pusher 72 enters the first state in which it has fully rotated around the arm rotation center ac in the direction of the arrow B. In this manner, the movement mechanism 80 causes the pressure mechanism 70 to transition only between the first state and the second state.

[0072] FIG. 10 is a cross-sectional view of the fixing device taken along line VII-VII in FIG. 3, showing the pressing mechanism in the second state. As shown in FIG. 10, in the second state, the pressure roller 31 presses the heat transfer member 65 against the base 381 of the holder 38 via the cylindrical body 37 and the heater unit 40 so that the heat transfer member 65 does not float from the base 381 of the holder 38. In this state, the heat transfer member 65 is restricted by the heat transfer member 65 from protruding from the hole 384 of the holder 38 toward the heater unit 40. In the first state, the force acting between the cylindrical body 37 and the pressure roller 31 is greater than that in the second state, so the pressure roller 31 presses the heat transfer member 65 against the base 381 via the cylindrical body 37 and the heater unit 40 so that the heat transfer member 65 does not float from the base 381 of the holder 38. In all states that can be transitioned to by the operation of the movement mechanism 80, the heat transfer member 65, the heater unit 40, and the temperature sensitive element 60 are pressed against the holder 38 by the pressure roller 31 and are immobile relative to the holder 38.

[0073] The functional configuration of the control unit 6 will be described. FIG. 11 is a block diagram showing a functional configuration of the control unit. As shown in FIG. 11, the control unit 6 includes a heating control unit 94, a pressurization control unit 95, a counting unit 96, and a drive control unit 97.

[0074] The heating control unit 94 energizes the heater unit 40 in the heating mode and stops energizing the heater unit 40 in the stop mode. The heating control unit 94 measures the temperature of the heat generation area 45 using the heater thermometer 61 when the fixing device 30 is started. If the temperature of the heat generation area 45 is lower than a predetermined temperature, the heating control unit 94 causes the heat generation area 45 to generate heat for a short period of time before the pressure roller 31 starts to rotate. The heat generated by the heat generation area 45 reduces the viscosity of the grease 47 applied to the inner circumferential surface of the cylindrical body 37. This ensures the slidability between the heater unit 40 and the cylindrical body 37 when the pressure roller 31 starts to rotate.

[0075] The heating control unit 94 measures the temperature of the heat transfer member 65 by the heater thermometer 61 during operation of the fixing device 30. The heating control unit 94 controls the supply of electricity to the heat generating region 45 based on the result of the temperature measurement of the heat transfer member 65. This allows the temperature of the heat transfer member 65 in contact with the holder 38 to be maintained below the heat resistance temperature of the holder 38.

[0076] When the fixing device 30 is in operation, the heating control unit 94 measures the temperature of each part in the y direction of the cylindrical body 37 using the film thermometer 64. The heating control unit 94 controls the supply of electricity to the heat generating region 45 based on the temperature measurement results of each part in the y direction of the cylindrical body 37.

[0077] The pressurization control unit 95 controls the moving mechanism 80. The pressurization control unit 95 controls the driving source 83 of the moving mechanism 80 to transition the pressurization mechanism 70 between the first state and the second state. The pressurization control unit 95 determines whether the state is the first state or the second state based on the detection result of a sensor that detects the rotation angle of the cam 82, and stops driving the driving source 83 that rotates the cam 82. When the temperature detected by the heater thermometer 61 is equal to or lower than a predetermined value in the stop mode of the heating control unit 94, the pressurization control unit 95 controls the driving source 83 of the moving mechanism 80 to transition the pressurization mechanism 70 to the second state.

[0078] The counting section 96 counts at least one of the transitions from the first state to the second state and the transitions from the second state to the first state. The drive control unit 97 restricts the transition to the second state when the count of the count unit 96 is equal to or greater than a predetermined value.

[0079] In this embodiment, the pressure mechanism 70 can transition between a first state in which the fixing nip FN is formed by the cylindrical body 37 and the pressure roller 31, and a second state in which the cylindrical body 37 and the pressure roller 31 are in contact with each other and the force acting on the cylindrical body 37 and the pressure roller 31 is smaller than that in the first state. With this configuration, the heat-generating sliding member 36 held by the holder 38 is not displaced when transitioning between the first state and the second state. Since the heat-generating sliding member 36 is not displaced, the fluctuation of the load applied to the heater thermometer 61 in contact with the heat-generating sliding member 36 can be suppressed. Therefore, the deterioration of the internal element of the heater thermometer 61 can be suppressed, and the durability of the fixing device 30 can be improved. The above effect is significantly obtained when the heater thermometer 61 is a thermistor.

[0080] The moving mechanism 80 has a cam 82 in which a small diameter portion 842, which has the smallest outer diameter of the cam surface 84, abuts against the cam follower 81 in the second state. With this configuration, the cam follower 81 is closest to the cam rotation center cc of the cam 82 in the second state. Therefore, even if the cam 82 rotates only in one direction, the pressure mechanism 70 can only take a state between the first state and the second state when the cam 82 is rotated, regardless of the rotation angle of the cam 82. Therefore, it is possible to reliably prevent the heat-generating sliding member 36 from being displaced when the cam 82 is rotated.

[0081] The holder 38 holds the heat-generating sliding member 36 so that a gap is formed between the heat-generating sliding member 36 and the holder 38 when the pressure roller 31 is separated from the cylindrical body 37. With this configuration, when the pressure roller 31 is separated from the cylindrical body 37, the heat-generating sliding member 36 is displaced, causing a change in the load on the heater thermometer 61. Therefore, the fixing device 30 of this embodiment is suitable for obtaining the above-mentioned effect, since the cylindrical body 37 and the pressure roller 31 are in contact with each other even in the second state to regulate the displacement of the heat-generating sliding member 36.

[0082] A heat transfer member 65 is disposed between the base 381 of the holder 38 and the heater unit 40. With this configuration, the number of parts that are deformed or displaced due to changes in the pressure of the pressure roller 31 against the film unit 35 increases compared to a configuration without a heat transfer member. This increases the number of factors that cause load fluctuations in the heater thermometer 61, which may accelerate deterioration of the internal elements of the heater thermometer 61. Therefore, the fixing device 30 of this embodiment is suitable for obtaining the above-mentioned effects, since the displacement of the heat-generating sliding member 36 is regulated.

[0083] The displacement of the heat-generating sliding member 36 is restricted by the pressure roller 31 when the heat-generating sliding member 36 transitions between the first state and the second state. This configuration can suppress the fluctuation of the load applied to the heater thermometer 61. Therefore, the above-mentioned advantageous effects can be achieved.

[0084] The heat-generating sliding member 36 is held by the holder 38 outside the heat-generating region 45 in the axial direction. With this configuration, when the pressure roller 31 is separated from the film unit 35, the heat-generating sliding member 36 can be pushed by the heater thermometer 61 and bend, and the load applied to the heater thermometer 61 fluctuates as the heat-generating sliding member 36 bends. Therefore, the fixing device 30 of this embodiment is suitable for obtaining the above-mentioned effects, since the cylindrical body 37 and the pressure roller 31 are in contact with each other even in the second state to regulate the displacement of the heat-generating sliding member 36.

[0085] The heat-generating sliding member 36 is pressed toward the pressure roller 31 by the heater thermometer 61. With this configuration, when the heat-generating sliding member 36 is displaced, the load applied to the heater thermometer 61 that presses the heat-generating sliding member 36 varies. Therefore, the fixing device 30 of this embodiment is suitable for obtaining the above-mentioned effect, since even in the second state, the cylindrical body 37 and the pressure roller 31 are in contact with each other to regulate the displacement of the heat-generating sliding member 36.

[0086] The cylindrical body 37 has a contact portion 371 that contacts the heat-generating sliding member 36 when separated from the pressure roller 31. When separated from the pressure roller 31, the cylindrical body 37 forms a gap between the heat-generating sliding member 36 and the contact portion 371, which expands from the contact portion 371 toward the outside in the y direction. With this configuration, when the pressure roller 31 is separated from the cylindrical body 37, the cylindrical body 37 is pressed by the heat-generating sliding member 36 and deforms to form a gap with the heat-generating sliding member 36. Therefore, in the fixing device 30 of this embodiment, even in the second state, the cylindrical body 37 and the pressure roller 31 are in contact with each other, which restricts the deformation of the cylindrical body 37 together with the displacement of the heat-generating sliding member 36, and therefore deterioration of the cylindrical body 37 due to repeated deformation can be suppressed.

[0087] When the temperature detected by the heater thermometer 61 is equal to or lower than a predetermined value, the pressure control unit 95 controls the drive source 83 of the moving mechanism 80 to put the pressure mechanism 70 into the second state. This configuration makes it possible to prevent the pressure mechanism 70 from transitioning to the second state in a situation where the temperature detected by the heater thermometer 61 is higher than the predetermined value and there is a high possibility that the fixing device 30 will be used soon. Therefore, frequent operation of the moving mechanism 80 is suppressed, and deterioration of the internal element of the heater thermometer 61 can be more effectively suppressed.

[0088] The counting unit 96 counts at least one of the transitions from the first state to the second state and the transitions from the second state to the first state. The drive control unit 97 controls the moving mechanism 80. The drive control unit 97 restricts the transition to the second state when the count of the counting unit 96 is equal to or greater than a predetermined value. This configuration makes it possible to prevent the degree of deterioration of the internal element of the heater thermometer 61 from exceeding a certain standard. Therefore, it is possible to prevent the heater thermometer 61 from breaking down due to its lifespan.

[0089] The control unit 6 may control each unit of the image forming apparatus 1 to limit the process of forming an image on the sheet S in the second state. With this configuration, it is possible to prevent the sheet S from being conveyed to the fixing device 30 in a state in which the fixing nip FN is not formed.

[0090] In the first embodiment, the heat-generating sliding member 36 has the heat-transfer member 65, but the heat-generating sliding member does not have to have a heat-transfer member. In this case, the temperature-sensing element 60 is provided so as to be in contact with the heater unit 40. With this configuration, no gap is formed between the heater unit 40 and the base 381 of the holder 38 in any state between the first state and the second state, thereby achieving the above-mentioned advantageous effects.

[0091] Second embodiment A heater unit 240 according to the second embodiment will be described with reference to Fig. 12. The configuration other than that described below is the same as that of the first embodiment. Fig. 12 is a bottom view of the heater unit according to the second embodiment.

[0092] The second embodiment differs from the first embodiment in the arrangement of the heat generating element 250 of the heater unit 240. The heater unit 240 has a heat generating area 245 and a wiring set 255 instead of the heat generating area 45 and the wiring set 55 of the first embodiment.

[0093] The heat generating region 245 is disposed on the substrate 43. The overall outer shape of the heat generating region 245 is formed into a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. The heating region 245 has a plurality of heating elements 250. The plurality of heating elements 250 has a pair of a first heating element 251, a second heating element 252, and a third heating element 253. The plurality of heating elements 250 are arranged in the x direction in the order of one first heating element 251, the second heating element 252, the third heating element 253, and the other first heating element 251. The longitudinal direction of each heating element 250 is the y direction. Each heating element 250 has a length corresponding to various sheet widths. The second heating element 252 is shorter in the y direction than the first heating element 251. Both ends of the second heating element 252 in the y direction are located inside both ends of the first heating element 251 in the y direction. The third heating element 253 is shorter in the y direction than the second heating element 252. Both ends of the third heating element 253 in the y direction are located inside both ends of the second heating element 252 in the y direction. Wires of a wiring set 255 are connected to each heating element 250. The heating area 245 generates heat when electricity is applied via the wiring set 255. The control unit 6 causes the corresponding heating element 250 to generate heat in accordance with the width of the sheet S passing therethrough.

[0094] In the second embodiment described above, the displacement of the heat-generating sliding member 36 including the heater unit 240 is restricted, and therefore the same effects as in the first embodiment are achieved.

[0095] (Third embodiment) A heater unit 340 according to the third embodiment will be described with reference to Fig. 13. The configuration other than that described below is the same as that of the first embodiment. Fig. 13 is a bottom view of the heater unit according to the third embodiment.

[0096] The third embodiment differs from the first embodiment in the arrangement of a heat generating element 350 of a heater unit 340. The heater unit 340 has a heat generating area 345 and a wiring set 355 instead of the heat generating area 45 and the wiring set 55 of the first embodiment.

[0097] Heat generating region 345 is disposed on substrate 43. The overall external shape of heat generating region 345 is formed into a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. The heat generating region 345 has a plurality of heat generating elements 350. The plurality of heat generating elements 350 has a pair of first heat generating elements 351 and a pair of second heat generating elements 352. The plurality of heat generating elements 350 are arranged in the x direction in the order of one first heat generating element 351, the second heat generating element 352, and the other first heat generating element 351. The y direction is the longitudinal direction of each heat generating element 350. The first heat generating element 351 becomes thicker from the center toward the end in the y direction. Both ends of the pair of first heat generating elements 351 are located at approximately the same position as each other in the y direction. The second heat generating element 352 becomes thinner from the center toward the end in the y direction. Both ends of the second heat generating element 352 are located at approximately the same position as both ends of each first heat generating element 351 in the y direction.

[0098] Wiring of the wiring set 355 is connected to each heating element 350. The heating area 345 generates heat by being energized through the wiring set 355. The control unit 6 controls the corresponding heating element 350 to generate heat according to the width of the sheet S passing through. When only the first heating element 351 is energized, the heat amount of the heating area 345 decreases from the center to the end in the y direction. On the other hand, when the pair of the first heating element 351 and the second heating element 352 are energized simultaneously, the heat amount of the heating area 345 is averaged over the entire length in the y direction compared to when only the first heating element 351 is energized. Therefore, when a sheet S having a smaller width passes through, the control unit 6 energizes only the first heating element 351. When a sheet S having a larger width passes through, the control unit 6 energizes the first heating element 351 and the second heating element 352.

[0099] In the third embodiment described above, the displacement of the heat-generating sliding member 36 including the heater unit 340 is restricted, and therefore the same effects as in the first embodiment are achieved.

[0100] In the above embodiment, the pressure mechanism 70 presses the pressure roller 31 toward the cylindrical body 37, but the present invention is not limited to this configuration. The pressure mechanism may be configured to press a film unit having a cylindrical body toward the pressure roller.

[0101] In the above embodiment, the first surface 41 of the heater unit 40 contacts the inner surface of the cylindrical body 37, but this configuration is not limited to this. The heat-generating sliding member may have a heat-equalizing member interposed between the first surface of the heater unit and the inner circumferential surface of the cylindrical body. In this case, the heat-generating sliding member does not need to have a heat transfer member interposed between the heater unit and the holder.

[0102] According to at least one of the embodiments described above, the pressure mechanism can transition between a first state in which the fixing nip is formed by the cylindrical body and the pressure roller, and a second state in which the cylindrical body and the pressure roller are in contact with each other and the force acting on the cylindrical body and the pressure roller is smaller than that in the first state. With this configuration, the heat-generating sliding member held by the holder is not displaced when transitioning between the first state and the second state. Since the heat-generating sliding member 36 is not displaced, the fluctuation of the load applied to the heater thermometer can be suppressed. Therefore, the deterioration of the internal element of the heater thermometer can be suppressed, and the durability of the fixing device can be improved.

[0103] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0104] 30... fixing device, 31... pressure roller, 36... heat-generating sliding member, 37... cylindrical body, 38... holder, 45, 245, 345... heat-generating area, 61... heater thermometer (sensor), 70... pressure mechanism, 80... movement mechanism, 81... cam follower, 82... cam, 83... drive source, 84... cam surface, 371... contact portion, 842... small diameter portion, FN... fixing nip (nip)

Claims

1. A film-like cylindrical body; a heat-generating sliding member disposed inside the cylindrical body, the heat-generating sliding member having a heat-generating region that generates heat when electricity is applied thereto, the heat-generating sliding member being arranged in an axial direction of the cylindrical body as a longitudinal direction; a holder for holding the heat-generating sliding member; a sensor that contacts the heat-generating sliding member to detect the temperature of the heat-generating sliding member; a pressure roller that contacts an outer circumferential surface of the cylindrical body to form a nip between the cylindrical body and the pressure roller; a pressure mechanism capable of transitioning between a first state in which the nip is formed by the cylindrical body and the pressure roller, and a second state in which the cylindrical body and the pressure roller are in contact with each other and a force applied between the cylindrical body and the pressure roller is smaller than that in the first state; a moving mechanism that causes the pressure mechanism to transition between the first state and the second state; A fixing device comprising:

2. the pressure mechanism supports the pressure roller so as to be rotatable about its axis and moveable along a direction perpendicular to the axial direction; The moving mechanism includes: A cam follower disposed in the pressure mechanism; a cam having a cam surface that contacts the cam follower and is rotatable about its axis, the cam moving the pressure roller in the perpendicular direction via the pressure mechanism in cooperation with the cam follower, and a small diameter portion of the cam surface that has the smallest outer diameter contacting the cam follower in the second state; A drive source that rotates the cam in one direction; having The fixing device according to claim 1 .

3. the holder holds the heat-generating sliding member such that a gap is formed between the heat-generating sliding member and the holder in a range overlapping with the heat-generating region in the axial direction when the pressure roller is separated from the cylindrical body. The fixing device according to claim 1 or 2.

4. the heat-generating sliding member includes a heater unit and a heat transfer member, the heat transfer member being between the heater unit and the holder; The fixing device according to claim 3 .

5. the heat-generating sliding member is held by the holder outside the heat-generating region in the axial direction; The fixing device according to claim 3 .

6. the sensor is biased toward the heat-generating sliding member with respect to the holder, the heat-generating sliding member is pressed toward the pressure roller by the sensor; The fixing device according to claim 5 .

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